1. Field of the Invention
The present invention relates to a method for producing an artificial leather having excellent dyeability and advanced fluff-like property.
2. Description of the Related Art
Conventional methods for producing an artificial leather pertain to obtaining non-woven substrate from a fiber obtained by spinning polymeric material and obtaining the artificial leather by subjecting the non-woven substrate through a plurality of processing steps. It should be noted that to render the artificial leather being similar to genuine leather, the fiber for producing the non-woven substrate is preferably an ultrafine fiber.
Currently, there are two methods for producing the above-mentioned ultrafine fiber, one being a mixed spinning method and the other being a conjugate spinning method. Commonly speaking, the island in the fiber obtained by the mixed spinning method ranges from 0.01 to 0.0001 denier per filament, and it is impossible to obtain a fiber having more than 0.01 denier per filament. As the island has a low denier per filament, it is difficult to be dyed, which results in the difficulty for removing the sea between the islands. The islands in the fibers obtained in the conjugate spinning method range from 0.05 to 0.5 denier per filament, and it is impossible to obtain a fiber having less than 0.05 denier per filament. As the island has sufficiently high denier per filament, it is easy to be dyed. However, the high denier per filament brings the island to a surface with low gloss.
JP 63-243314 discloses a method for producing a fiber. The fiber is obtained by controlling the shear rate of polymers so that the island (referring to the big island) having larger cross-section in the fiber is homogeneously distributed in the central portions of the fiber and the island (referring to the small island) having smaller cross-section in the fiber is homogeneously distributed in the outer portions of the fiber. The fiber has high tenacity. However, due to the big island of the fiber thus obtained has lower than 0.02 denier per filament, it is not easy to dye the fiber. Furthermore, the high density of the small island brings difficulty for dissolving and removing the sea component of the fiber.
Taiwan Patent Application No. 78101985 discloses a method for producing an ultrafine fiber by conjugate spinning. The ultrafine fiber has an island having 0.3 to 0.05 denier per filament. Due to the limitation of diameter of the distribution plate of the spinneret, an island having consistent denier per filament is obtained. Hence, an artificial leather produced from the ultrafine fiber has poor feel and surface feather when compared to those of genuine leather.
Taiwan Patent Application No. 83109961 discloses a method for producing an ultrafine fiber by conjugate spinning, characterized by adding a polymer having different dissolving and removing property from that of the sea component into the sea component to form the island and dissolving and removing the sea component from the fiber thus obtained to produce a fiber having large island and small island simultaneously. However, the method pertains to a conjugate spinning process, which is tedious and complicated, and the fiber thus obtained has a small island having a size, which is too small to be easily dyed. Hence, the leather produced from the method still has surface not completely dyed.
Taiwan Patent Application No. 89121271 discloses a method for producing an ultrafine fiber by mixed spinning, in which the fiber has 0.0003 to 0.003 denier per filament. Due to the size of fiber island is small, it is difficult to dye the fibers and the fastness and leather tenacity is poor.
Accordingly, a mixed spinning process cannot produce an ultrafine fiber having about 0.01 to about 0.05 denier per filament and about 0.05 to about 0.5 denier per filament simultaneously.
Therefore, it is the purpose of the present invention to mitigate and/or obviate the drawbacks existing in the prior art in the manner set forth below.